1. Field of the Invention
The basic function of the organs, cells and molecules that comprise the immune system is to recognize and to eliminate foreign substances from the body. These foreign substances are eliminated by reaction between the foreign substance and antibodies which are formed in response to the substance. In general, this function is performed efficiently and without detriment to the host. However, in hypersensitive individuals, disturbances can occur which can lead to pathogenic disorders such as, an uncontrolled response, for example, allergic disorders.
Hypersensitive individuals undergo an "altered state" as a result of contact with the antigens from an allergen, leading to the formation of antibodies thereto. Subsequent contact with one of those antigens or a structurally similar substance can evoke in a hypersensitive individual a pathological reaction, due to the presence of such antibodies. When these individuals inhale or ingest the offending antigen, a prominent and common manifestation includes hay fever, asthma, urticaria ("hives") or dermatitis. The tendency to develop this form of allergy is hereditable.
Allergic responses are involved with the production within an individual of tissue-sensitizing IgE antibodies. These IgE antibodies have a high affinity for receptors on cells present in various body tissues. The receptors are on mast cells which are found in close association with capillaries in connective tissues throughout the body and on basophilic leukocytes (blood cells). Mast cells and basophils contain pharmacologically-active mediators or spasmogens, such as histamine, serotonin (5-hydroxytryptamine) and kinins (basic peptides) concentrated in cytoplasmic granules. Contact of the IgE antibodies, which are fixed to mast cells and basophils, with antigens can trigger cross-linking of the IgE antibodies. In turn, this cross-linking causes degranulation of mast cells and basophils, which release the chemical mediators and produce manifestations of the allergic response referred to earlier.
Allergy diagnosis can be accomplished in numerous ways. A frequency used method involves studying the patient's history, i.e., recent exposure to various allergens, and based on a decision regarding the identity of the suspected allergen, injecting small amounts of the suspected allergen into the skin, and examining the injected site for a reaction which is characterized by erythema and wheal formation and associated pruritus. This method is quick and easy for the clinician and considered to be a reliable indication of allergen sensitivity because it is conducted in vivo. However, this method can involve considerable patient discomfort, is difficult to conduct with children, can expose an extremely hypersensitive patient to danger, and may be difficult to interpret in patients with severe dermatitis.
When allergy to foods is suspected, dietary exclusion tests can be utilized. These tests are not convenient for the patient and can involve a lengthy procedure.
In vitro tests which involve specific binding assay methods are also used. A typical specific binding assay procedure is the determination of IgE antibodies in the blood of a hypersensitive individual. U.S. Pat. No. 3,720,760 is directed to a technique which measures allergen-specific IgE levels in serum by the radioallergosorbent test (RAST). This type of in vitro test is expensive and requires a sophisticated laboratory in addition to requiring about 36 hours to complete.